Woven and braided fabrics have been used to reinforce various devices. Compared to weaving, braiding may impart greater strength for a unit of weight. The strength of a braid comes from the fact that multiple yarns can be intertwined without any being twisted around another. Generally these are continuously braided at an angle and there is no need for any yarn to suffer a sharp bend. As a result, loads may be distributed evenly and efficiently throughout the braid.
Automated fabrication of braids generally results in tubular or flat configurations. Braids can also be formed without any underlying support (freestanding) or over a mandrel or a part to be reinforced, such as the mast of a sailboat. Braiding can also be done over a three-dimensional part, such as a tool.
A single braid can incorporate multiple yarn materials to form a hybrid weave. This is often done to make patterns in the resulting product. Yarns can be of metal, carbon fiber, glass fiber, mono or multifilament threads, etc. Braiding can be done with very delicate materials.
Braid has been used as a reinforcement for some surgical devices such as endoscopes and catheters and for implantable devices such as splints and stents.
Non-woven fiber reinforcements are also known, for example, randomly arrayed fibers such as in fiberglass and hand-laid fibers arrayed over and within a matrix are known strategies. Both have been described in connection with the reinforcement of medical balloons.
Many composite balloon structures are reinforced by inelastic filaments, which is a good match for folding to minimize the collapsed balloon's volume. However, the fiber can be an impediment to folding, an issue that is addressed by at least some of the inventive embodiments disclosed below.
The following are some references to background in the field of braiding technology. A brief overview and comparison of 2D and 3D braiding machines and the kinds of structures they can create is provided by an article, “Braiding,” 2005 Advanced Composite Materials & Textile Research Laboratory, University of Massachusetts-Lowell. [online] August 2007 [Retrieved on 2006 Jun. 21]. Retrieved from the Internet. <http://mechanical.uml.edu/acmtrl/research-Braiding.htm>.
The company, 3TEX, provides information about state of the art three-dimensional automated braiding at [online]] Retrieved on 2005 Jun. 21] Retrieved from the Internet <http://www.3tex.com/3braid.cfm>. The page shows photographs and an animation of a large Cartesian braiding machine. One of the points made is that with computer control, it is possible to shift the braiding pattern at any time without changing the number or continuity of the yarns.
A report by the National Textile Center (NTC) in Springhouse, Pa. discusses different kinds of braiding patterns such as diamond, regular, and Hercules braids and discusses behavior of braids under tensile load, the effect of yarn angle with respect to load and jamming condition, and other issues. “Engineered Non-Linear Elastic Blended Fabrics,” NTC Project F00-PH05 2005 [Retrieved on 2006 Jun. 21]. Retrieved from the Internet. <http://www.ntcresearch.org/pdf-rpts/AnRp02/F00-PH05-A2.pdf>
The following articles discuss braids with different mechanical properties, including mixing materials. “Analysis of three-dimensional textile preforms for multidirectional reinforcement of composites;” Guang-Wu Du, Tsu-Wei Chou and P. Popper; J. Mater. Sci. 26 (1991) 3438-3448. Dunn, Matthew; Armstrong-Carroll, Eileen; Gowayed, Yasser; “Engineered Non-linear Elastic Bland Fabrics” [Retrieved on 2006 Jun. 21]. Retrieved from the Internet. <http://wwvv.ntcresearch.org/pdf-rpts/Bref0601/F00-P05.pdf>.
The following article discusses the effect of braids on the mechanical properties of braided fabrics. There is considerable background on hybrid braids and their performance. Seneviratne, Waruna P. and Tomblin, John S.; “Design Of A Braided Composite Structure With A Tapered Cross-Section;” National Institute for Aviation Research Wichita State University Wichita, Kans. 67260-0093 The Department Of Defense Handbook Composite Materials Handbook Volume 2, “Polymer Matrix Composites Materials Properties,” discusses braids in the context of composite materials. [Retrieved on 2006 Jun. 21]. Retrieved from the Internet. <http://www.lib.ucdavis.edu/dept/pse/resources/fulltext/HDBK17-2F.pdf>